1. Field of the Invention
The present invention relates to an electric horn system. More specifically, the present invention relates to an improved diaphragm system for an electropneumatic horn system.
2. Description of the Related Art
The related art involves generally electric and electropneumatic horn constructions and systems. Electropneumatic horns are those which generate sound by generated air flow or compressed air and are considered (very broadly due to their typical electrical operation of compressed air or air-supply valving) to be within the wider grouping of electric horns due to the electric control of the generation of the air flow or compressed air. It should be noted that electric horn constructions also include (in addition to pneumatic sound creation) the creation of electronic sound (e.g. speaker type systems) wherein sound or tone is the result of an electronic signal to a speaker and not the result of an acoustic passage. As a consequence, those of skill in the art will recognize that the use of the phrases electronic, electrical, and electropneumatic shall be considered non-limiting in the following description.
Conventionally, electropneumatic horns include acoustic units consisting of a straight exponential tube of a length related to the frequency to be reproduced, inserted in an acoustic chamber in which a membrane free to move with a reciprocating motion is arranged and positioned. Also, the straight tube comprises a first stretch with generally constant cross-section, provided with an inlet mouth for the sound signal generated by the oscillating membrane and a second stretch having a section varying with a generally conic exponential law ending with an outlet mouth for the amplified sound signal (e.g., horn shaped).
As used in these conventional electropneumatic horns, the membrane is properly stretched or positioned during a pre-assembly calibration phase by deformation against the membrane of a member referred to as a ‘sound generator’ and applied to a chamber body, in such a way to generate a sound with manufacturer-desired predetermined acoustic pressure during a use. In an alternatively constructed versions of the related art, the acoustic units are paired (commonly bi-tonal), and the corresponding tubes are volute wound and juxtaposed to limit the overall dimensions of the horn allowing for reduced-size installations.
As already stated said acoustic horns and more particularly those with a straight acoustic tube (e.g., ‘truck air horns’), equip motor vehicles and are generally installed in the engine compartments and on vehicle roofs. Acoustic horns with different features are available on the market, both by others and by the present Applicant, and are mainly classified according to the number of acoustic units, generally one to a general maximum of three tuned tonal sounds, each shaped according to the frequency that each unit should reproduce.
The need to optimize space and reduce dimensions of every element of the motor vehicle, has lead to the reduction in size of such electropneumatic acoustic horns generally, and the miniaturization of specific horn components. For example, it is known to reduce the size of the air compressor unit or member as well as reduce the overall size of the acoustic sound units.
Referring now to U.S. Pat. No. 7,712,430, the entire contents of which are herein incorporated by reference, FIG. 1-3 show a conventional electropneumatic horn assembly showing the air venting channels 510. The horn 500 further comprises an electric compressor unit 506 having a compressor air inlet 513 and a compressor air outlet 513 for the supply of compressed air. Additionally, the assembly comprises a monolithic housing assembly 502 having a first housing portion embodying an opening defining a space for reception of the compressor unit 506 in the first housing portion 540, and a second housing portion 545 substantially housing a sound wave generator system. Further, the assembly comprises a plurality of air intakes on the bottom that allow air to be brought along the outer face 512 of the compressor unit 506. The face 512 of the compressor 506, when in use, radiates heat that heats the air moving along the outer face of the compressor 506. The assembly comprises a set of one or more vents 510, embedded in the monolithic housing assembly 502, for venting air from the metal face 512 of the compressor unit 506 for the purpose of reducing air temperature (cooling) across the surface of the compressor assembly 506. This cooling feature prevents burnout of the brushes, and metal fatigue of the compressor components.
The horn assembly comprises: at least one acoustic chamber 504 having an opening for introduction of compressed air; a membrane member provided with an opening for sound generation and at least one acoustic duct housed in the housing assembly and communicating between the at least one acoustic chamber and the at least one horn outlet to propagate sound generated by the membrane member outside the horn. There are also air channeling means for communicating between the compressor air outlet of the compressor unit and the opening of the at least one acoustic chamber. Such a horn assembly comprises means for permanently affixing the electric compressor unit in the housing assembly whereby the affixing means prevent removal of the electric compressor unit and improves operational stability of the housing assembly.
The acoustic chamber according to the prior art is constructed by compressing metal membrane member 506 onto outer housing member 508 by exerting force 514 as shown in FIG. 4. This compressed fit of membrane 506 onto outer housing 508 forms a diaphragm 522 (FIG. 5) for sound generation from the electric horn 500. Outer housing member 508 also includes an inlet opening 516 (FIG. 6) to allow air to enter the chamber formed between membrane 506 and outer housing 508. However, in such a device, unwanted particles such as particle 518 typically enter the chamber through inlet opening 516. Such unwanted particles may become lodged in chamber (see FIG. 6, particle 518A) such that they eventually cause membrane member 506 to deform at points of intersection of the membrane member 506 and outer housing 508 (FIG. 7). Deformities such as this negatively affect the sound emanating from the acoustic chamber.
What is not appreciated by the prior art therefore, is the need for an improved system comprising a diaphragm that is constructed in such a manner so as to substantially prevent the deforming of the membrane member within the acoustic chamber of the electropneumatic horn assembly without minimizing the operational reliability of the horn. Accordingly, there is a need for an improved diaphragm for an electropneumatic horn system, and more specifically an improved electropneumatic horn system that compensates for one or more of the detriments noted above.